Active carbon, production method thereof and polarizable electrode

Abstract

The present invention relates to an active carbon containing an alkaline earth metal compound inside the particle and having a specific surface area of 10 to 2,000 m 2 /g, which is suitable to be used for polarizable electrodes in an electric double layer capacitor. The active carbon of the present invention enables to increase the capacitance of an electric double layer capacitor as well as to control the expansion of electrodes. The active carbon of the present invention can be obtained by adding an alkaline earth metal compound to a material such as pitch and performing heat treatment and activation.

1. An active carbon comprising an alkaline earth metal compound in the inside of the particle and having a BET specific surface area of 10 to 2,000 m 2 /g as determined by a nitrogen adsorption method, and wherein the alkaline earth metal compound is a particle having a particle size of 10 μm or less,
 wherein 
 the content of the alkaline earth metal compound is from 30 to 100,000 ppm by mass, 
 the ratio of the peak height of D peak (1,360 cm  −1 ) to the peak height of G peak (1,580 cm −1 ) in the Raman spectrum is from 0.8 to 1.2, and 
 the volume of pores having a pore size of 20 to 50 Å is in the range of 0.02 ml/g or more as determined by the BJH method using the nitrogen adsorption method. 
 
     
     
       2. The active carbon as claimed in  claim 1 , wherein the alkaline earth metal compound is at least one alkaline earth metal compound selected from the group consisting of beryllium, magnesium, calcium, strontium, barium and radium. 
     
     
       3. The active carbon as claimed in  claim 2 , wherein the alkaline earth metal compound is at least one member selected from the group consisting of alkaline earth metal and oxides, hydroxides, chlorides, bromides, iodides, fluorides, phosphates, carbonates, sulfides, sulfates and nitrates of an alkaline earth metal. 
     
     
       4. The active carbon as claimed in  claim 1 , wherein the alkaline earth metal compound is at least one member selected from the group consisting of alkaline earth metal and oxides, hydroxides, chlorides, bromides, iodides, fluorides, phosphates, carbonates, sulfides, sulfates and nitrates of an alkaline earth metal. 
     
     
       5. The active carbon as claimed in  claim 4 , wherein the alkaline earth metal compound is calcium compound. 
     
     
       6. The active carbon as claimed in  claim 1 , which substantially does not contain a particle having an average particle size of 1 μm or less and/or 100 μm or more. 
     
     
       7. An active carbon wherein a porous carbon layer comprising non-graphitizable carbon is coated on the active carbon as claimed in  claim 1 . 
     
     
       8. The active carbon as claimed in  claim 7 , wherein the volume of pores is in the range of 0.01 to 1.55 ml/g as determined by the nitrogen adsorption method. 
     
     
       9. The active carbon as claimed in  claim 7 , having an average particle size of 3 μm to 70 μm. 
     
     
       10. A polarizable electrode comprising the active carbon as claimed in  claim 1 . 
     
     
       11. A polarizable electrode comprising the active carbon as claimed in  claim 1  and a vapor grown carbon fiber. 
     
     
       12. The polarizable electrode as claimed in  claim 11 , wherein the vapor grown carbon fiber has a hollow structure and has an outer diameter of 2 to 500 nm and an aspect ratio of 10 to 15,000. 
     
     
       13. The polarizable electrode as claimed in  claim 11 , wherein the vapor grown carbon fiber has a pore volume of 0.01 to 0.4 ml/g and a BET specific surface area of 30 to 1,000 m 2 /g as determined by the nitrogen adsorption method. 
     
     
       14. The polarizable electrode as claimed in  claim 11 , wherein the spacing of the (002) face of the vapor grown carbon fiber, d 002 , is 0.3395 nm or less. 
     
     
       15. The polarizable electrode as claimed in  claim 11 , wherein the vapor grown carbon fiber is a branched fiber and the hollow structure of the branched part communicates with each other. 
     
     
       16. The polarizable electrode as claimed in  claim 11 , wherein the vapor grown carbon fiber is mixed in the amount of 0.1 to 20 mass % of the carbon powder material. 
     
     
       17. The polarizable electrode as claimed in  claim 11 , wherein the vapor grown carbon fiber is fusion bonded to the surface of the active carbon. 
     
     
       18. An electric double layer capacitor comprising the polarizable electrode as claimed in  claim 10 . 
     
     
       19. The electric double layer capacitor as claimed in  claim 18 , which contains an organic electrolytic solution obtained by dissolving an electrolyte in an organic solvent. 
     
     
       20. A slurry containing the active carbon as claimed in  claim 1 . 
     
     
       21. A paste containing the active carbon as claimed in  claim 1 . 
     
     
       22. An electrode plate, wherein the active carbon as claimed in  claim 1  is applied on the surface. 
     
     
       23. An energy device containing an electric double layer capacitor as claimed in  claim 18 .